Skin the fish and remove any bones. Cut the flesh into bitesize pieces. Pat dry with kitchen paper and set aside.

Grind shrimp paste, onions, ginger, galangal, garlic and fresh chillies to a paste.

Heat 2 tbsp of oil and fry the spice mixture, stirring, until it gives off a rich aroma. Add soy sauce. Strain the tamarind and add the juice. Add the water and cook for 2-3 minutes.

In a separate pan, fry the fish in remaining oil for 2-3 minutes. Turn once only, so that the pieces stay whole. Put pieces in sauce and cook for another 3 minutes.

Put in a bowl and garnish with celery leaves or a little chopped fresh chilli.